Comfortable wearing apparel allows moisture which is naturally evaporating from the skin to dissipate so there is never a buildup of high humidity or liquid moisture near the skin area. Failure of the apparel to allow this moisture to dissipate causes the body to feel hot and uncomfortable in the area the apparel covers. The dissipation of moisture vapor can occur in a number of ways: into the ambient air through openings in the apparel; into ambient air through the materials making up the apparel, or in the case of leather, a limited amount of moisture vapor can be absorbed spontaneously within the leather to reduce humidity buildup.
There are methods of measuring the rate of moisture transmission and absorption of wearing apparel, but wearing apparel such as footwear, gloves and hats are not ordinarily, easily and inexpensively tested for their moisture vapor transmission properties. This is especially true of footwear, such as, shoes and boots. For most shoes and boots, perhaps the most important mechanism for dissipating humidity in the microclimate near the foot is diffusion of moisture vapor from the inside of the shoe, through the shoe materials, to the external environment. There has not been an easy, inexpensive way to measure these properties of a finished shoe or boot. While actual wear tests by human subjects can be used to determine the comfort level of a shoe, such tests require a strict test protocol for accurate results, are time-consuming to perform, and are consequently expensive. The materials used in manufacturing shoes can presently be tested for their ability to transmit moisture through them by a variety of techniques, one of which is ASTM-E96-B 66B, and another method which can be used for waterproof materials only is described in U.S. Pat. No. 4,194,041 at column 7 lines 28 through 48. These methods are useful for determining the moisture vapor transmission rate (MVTR) of materials available in sheet form such as leather and shoe fabric. However, in the construction of a footwear article, these materials are stretched or deformed into other shapes. Such deformation processes can affect the MVTR by changing the microstructure of the materials as well as by changing the thickness and shape. There is also concern about the deleterious effect adhesives used in footwear construction may have, since most adhesives have low MTVR when tested as a coherent film of adhesive. Also, it would seem that the overall MVTR of a shoe would be adversely affected by the bits and pieces of very low MVTR materials that are often used, such as plastic or metal heel and toe supports as well as certain decorative pieces. Even given the exact knowledge of the geometry, position, and MVTR of each component in a shoe, it is not obvious how to calculate what the overall rate of moisture transmission from the shoe will be. A method for measuring the moisture transmitted through a finished shoe is of great value; especially when such a method is non-destructive to the footwear article so that it can be used for manufacturing quality control; especially when the test apparatus is not expensive; and, especially when the method yields repeatable quantitative results that correlates with footwear comfort.